


Nøkken

by Elphen



Category: Sherlock (TV)
Genre: Folklore, M/M, Mythical Beings & Creatures, Obsession
Language: English
Status: In-Progress
Published: 2014-05-16
Updated: 2014-06-21
Packaged: 2018-01-25 09:03:20
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 3,492
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1643000
Author URL: https://archiveofourown.org/users/Elphen/pseuds/Elphen
Summary: <blockquote class="userstuff">
              <p>AU. Sherlock lives alone, dividing his time between solving cases and playing the violin. On a case up in the Dales he attracts the attention of a mythical being. He encounters it again in the guise of a seemingly unremarkable man and is offered a deal. The consequences might be more than he bargained for, but is he able to handle it?</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> Apologies for the summary, it is not something I'm good at.  
> An idea that would not leave me alone. Where it will lead me I am not quite sure, but we shall see. It is somewhat based on the stories of the Nøkken I was told as a child.
> 
> No beta or britpicker, mistakes and strange ideas are all mine (and the rating shall fit in time)

The first time he saw it was on the bank of a small river up in the Dales one late November day. It was nothing more than a fleeting glimpse out of the corner of his eye at first and he thought he might have imagined it. He had himself convinced that it had been a trick of the light that was fading over the grassy moors by the time he saw it again, having moved further up the river.

It was still fleeting and it could easily be dismissed as something imagined, though it was starting to tickle his curiosity. Night was falling fast, however, and with it his chance of getting back to the godforsaken village he was staying in for the case, so he put it out of his mind as he started walking back, following the water as he had on the way out.

Due to a slight miscalculation on the manoeuvrability on grassy, uneven terrain with fading visibility, he was still on his way when the last of the light faded. As it did, he saw it once again, out of the corner of his eye but for longer than before. It was hard to discern in the darkness, but the outline of what could be a man seemed to be standing out in the water.

Then he blinked and the vision was gone. He didn’t bother waiting to see if it would appear again. Instead he continued walking, his frustration that he had not gained the information he had come up for exacerbated by the birds that seemed to sing louder as the sun went down.

What he didn’t notice in his beginning strop was that the song had a melody and cadence to it that was rather…sophisticated for birds.

 

* * *

 

It was early January and he was crouching by the remnants of a crime scene, gathering the information he could after most had already been destroyed by idiot SOCOs. He couldn’t even blame it on Anderson, as it had been a different team and another DI that had been in charge of this case originally. Only when it was passed to Lestrade due to difficulty was Sherlock allowed in.

Not that he hadn’t solved most of the case already – the disappearance of young boys who turned up dead because they had fought and lost in illicit boxing matches, how utterly _dull_ – but there was something that had been bugging him about the scene of crime findings, which admittedly were incompetent, and so there he was, alone as he searched for the piece of evidence that was missing.

The grey din that was the amount of daylight you got in the city on an overcast winter day was not making it easier to spot, unfortunately, even with his skills and his pocket magnifying glass. By all measures, it should still be there, given the tide didn’t go that far up the bank and it would have been stuck somewhere.

A hand –somewhat broad, slightly stubby and tanned, but clean, with some rather...particular calluses covering the palm – appeared in his vision, holding the object he’d been looking for; the stud earring that had been the marker of who the boxer was fighting for and had been ripped out rather forcefully sometime after death.

He grabbed the stud from the hand proffering it, but didn’t look up before he had secured it in his coat pocket, only to find that the man was no longer in front of him. Standing up, he looked around to see what direction the man had taken, but failed to spot him anywhere.

Frowning, he started walking rather briskly back towards home. He didn’t waste his breath by calling out; if the man could disappear out of sight as quickly as that, he would be long gone and there would be little point in shouting.

It was several streets away from the bank that he became aware that he was humming under his breath, a melody he knew well, but hadn’t played in years. What part of his mind palace that had been dragged from he didn’t bother examining. He stopped humming instantly, however.

 

* * *

 

 

He was lying on the sofa, dressing gown twisted around and under him as a result of his twisting. His hands were steepled under his chin, fingers tapping against each other in the melody he’d previously hummed as he contemplated.

It had been over a week since he’d retrieved the earring from the river bank and since then there had been no cases worthy of any interest. Instead he’d been cooped up in the flat, doing experiments and, much to his annoyance, eventually ending up playing that damn tune whenever he picked up his violin in order to think. It wasn’t even as if it was any particular brilliant or advanced piece.

To be honest, the only reason he was able to recall it at all was that it was the first piece that he managed to master when he was a child. He had deleted most of the associated experiences, but the pride and the piece had stuck in his Mind Palace, much to his consternation. It was nothing but useless data.

At some point he must have fallen asleep, since he started at the sound of a bow being dragged across some strings. The sound itself wasn’t shrill or sharp or anything that should cause attention except for the fact that it was otherwise silent in the flat.

Vision slightly blurry from sleep, he managed to focus on where the sound was coming from and saw a man, sitting in the chair that held the Union Jack pillow, no instrument under his chin, but held in one hand and bow in the other, looking back at him.

It wasn’t a particularly noteworthy man. You wouldn’t point him out in the street or necessarily remember his face half an hour after you’d seen him. He was average. Normal. Except...

Except for the eyes. It was hard to tell in the limited light from the lamps outside streaming through the curtains in the otherwise dark flat, but something seemed off somehow. It would require further investigation.

Sherlock turned himself so he could get a better look, but did not rise from his place on the sofa. The intruder regarded him silently, face calm and just the tiniest bit of a smile lurking at the corner of his mouth. He did not look frightened that he’d been caught or as if he was intending to defend himself. Interesting.

“There are more valuable things here.”

“I beg your pardon?” The voice, too, was average though soft and pleasantly masculine. There was something else to it, though; something like a soft echo trailing after the words, like the dying vibrations of a string being plucked.

“If you intended to break in here to steal, there are far more valuable things in here than my violin,” Sherlock said curtly, always annoyed at having to repeat himself in any way. “The telescope for one, not to mention the chemicals. Quite apart from the fact that sitting in a chair in the house you’re stealing from and playing it seems particularly moronic, yet you don’t strike me as an imbecile. So...explain.”

“You are wrong,” the man said finally, after something of a pause. At Sherlock’s annoyed frown, the corner of his mouth quirked into a half-smile. “About your violin, that is. It is a beautiful instrument.”

“Yes, of course it is!” Sherlock snapped. “I never said anything to the contrary. But a useful instrument, a _beautiful_ instrument does not equal an instrument of any value except to its owner.”

That got him a low chuckle, which only served to annoy him further.

“Get out,” he said coldly as he sat up, having had quite enough of his night time burglar. “If that’s what you want, take the blasted violin, but get out of here _now_.”

Infuriatingly, the man didn’t move out of the chair. But he did lay down the instrument on the table, with an air of reverence that struck the brunette as odd even amidst his anger.

“A beautiful instrument deserves a skilled master.” The man kept his eyes on the violin.

_Are you inferring that I am not?_ Sherlock wondered as he continued to glare at the intruder. “I do believe I told you to leave my flat. Are you an imbecile after all or just _selectively_ deaf?”

The man looked up then and Sherlock nearly let out a gasp. There had been something odd about the eyes before, but now they seemed as if, and it was a notion he would later scoff at, there were coals smouldering in the pupils.

The voice twanged with the echo of strings.

“Do you want to become skilled?”


	2. Chapter 2

**Summary for the Chapter:**

> When the mysterious guest leaves, Sherlock is quite happy to believe it never happened. Things are not that simple, though, and the man does return

**Notes for the Chapter:**

> Thank you to people for commenting and leaving kudos. Means a lot.
> 
> Still no beta or britpicker ;)

Inwardly, a part of Sherlock bridled. The man was not merely _inferring_ that he lacked skill; he was saying it out loud, plain and simple. The cheek of it! Another, larger part of him was curious, however, as to why this obviously mad man was really here, if not to burgle him. The idea of the man actually being there in order to teach him was enormously preposterous, but it might merit some further investigation, along with the odd cadence to the voice.

“I should take offense at the implication that I need teaching,” he replied, voice remaining calm, though slightly frosty.

“Even the best virtuoso can need teaching,” the stranger said in a voice reminiscent of an adult gently chiding a child, “and there is always something new to learn; though I notice you don’t seem to take offense, either.”

The detective stood abruptly, feigning indignation as he turned around to face the windows. “And you would know that how exactly?”

There was no answer. He looked over his shoulder and the seat the man had been occupying was as empty as it normally was. There was no sign of him anywhere in the room and no doors had been opened, never mind the fact that no one could move that fast or that silently.

Something trickled out of his Mind Palace and he was suddenly back at the river bank, being handed the earring. Then he hadn’t taken notice of anything besides the hand and what it held, but he had filed away the fact that the one helping him had taken off without any trace of him either.

For a while he stood there, frowning as he tried to puzzle out how exactly a man could move like that or what trick of his ears was at work to make him hear musical twangs in the echo of the man’s voice.

He was brought out of his musings by a call from Lestrade, offering a case with a dead body with parts belonging to several different people and no sign of surgery. Eager to finally have a case, he managed to insult the inspector three times before deigning to at least have a look at the crime scene. He threw on clothes as fast as he could and almost leapt his way down the stairs, ignoring the shouts of Mrs Hudson as he went.

Blue-grey eyes watched him as he went.

 

* * *

 

For the next two weeks, he was occupied with a case that involved several more bodies, an interrogation of a surgeon that drugged him, a chase through the tunnel system of the Underground and a culminating...incident in an abattoir. It was good; stimulating and fulfilling and nothing else mattered.

After the case, he collapsed, quite literally. The human body was not designed to be without sustenance or sleep for extended periods of time and it would not endure it without some consequences. He cursed it as he lay in his bed, limbs too weary to obey his will to move.

He sometimes felt a dip in the bed or a hand on his shoulder as he slept, but when he woke, he dismissed it as being conjured by his mind. As he staggered into the kitchen, he found a cup of cold tea on the counter and a pile of cucumber sandwiches covered by plastic foil in the refrigerator, as far away from any kind of body part as possible. He smiled slightly. Thank the heavens for Mrs. Hudson.

The case had given him ample new ideas for experiments to be carried off and so he found plenty to occupy his time and, more importantly, his mind. Sometimes he would sit and think and he would find his eyes had drifted to the violin, still lying and gathering dust on the table where it had been left when...

He almost flung himself back into his experiments every time it happened, busying himself with measuring, calculating, prodding and dissecting.

 

* * *

 

 

“Perhaps I should have taken it.”

The voice, echoing in the dead silence of the flat, startled him, though not enough for it to be obvious or disrupt the sample he’d been examining under the microscope. It was delicate and he’d been working on it for a while.

He pointedly remained immobile as he answered. “Perhaps. You have certainly had ample opportunity to do so in the intervening time, given your apparent ability to go in and out of here without any kind of sound or sense of movement.” He turned around to face his intruder. “So the question is; why haven’t you?”

The man was standing in the sitting room, close to the chair he had sat in previously. He seemed to be wearing the same, unassuming plaid shirt and trousers as well. There was the sense of déjà vu.

Once again, the man seemed reluctant to answer any direct questions put to him. “It isn’t right for an instrument to be neglected so. It needs to be cared for.” He picked up the violin as he spoke, running his fingers over the wood, reverently.

Sherlock paused, eyes narrowed. “I seem to recall you claiming you could...’teach me’ and yet you have been non-existent for over a month. Not that it matters.” He managed to add that last sentence without betraying his slight hint of disappointment. The man had been an interesting occurence.

His night time guest looked up at him, smiling, and he was again made aware of the eyes that seemed normal yet weren’t quite...right.

“I cannot teach someone who doesn’t agree to it,” hesaid solemnly. “That is not how it works.”

“Then how _does_ it work, pray?” Sherlock snapped, moving into the sitting room. “Oh, of course. I suppose I have to pay you first – do you take pound notes?”

The smile on the other’s face faded and was replaced with an expression that was a mix of disappointment, disbelief and a hint of frustrated annoyance. “What exactly do you think I am?”

“Apart from a persistent and slightly deranged intruder?” the consulting detective asked.

To his surprise, the smile returned and there was a slight chuckle, which quivered with the aftershocks of plucked strings. “Apart from that, yes.”

Sherlock drew in a breath, ready to launch into one of his deductions after casting another glance at the man, but then he...stopped. It was the eyes. They stopped his voice dead in its tracks and drew him in, as hard as he tried not to be affected.

Eventually, after what seemed like an eternity, he was able to blink and found that in his mental absence the man had moved closer and held out the violin. It almost seemed like a peace offering.

Sherlock grabbed it, but the other man didn’t let go.

“You didn’t answer my question.”

He was almost drawn in again, but this time he had the sense to focus his gaze just off to the side. “You clearly want me to believe you’re something you’re not. How you do it...” he trailed off, not wanting to let on that he hadn’t yet worked out how the man was doing it.

There was that chuckle again. Despite the strangeness and the lingering annoyance, a part of Sherlock found itself liking the sound and wanted to hear it again. As much as he possibly could.

“Always the detective, aren’t you? Always the sceptic, looking for the strings and the mirrors in everything you see.” The man let go of the violin and took a few steps back. The sound of rushing water seemed to filter in from around them, growing until it filled Sherlock’s head to capacity, roaring in its tide, making it hard to concentrate on anything else, though he tried.

When it receded and he was again capable of comprehending anything outside the pounding of his ears, he found the man now holding a violin of his own, shrouded in shadows, even though there was plenty of light in the flat.

“Impossible.” The word was out of his mouth before he could stop it.

“Perhaps. But true nevertheless.” The bow pulled over strings ever so slowly in a move that should have sounded dissonant, but was merely a pleasant, but dangerous hum. It was a fitting accompaniment to the voice. “I was going to wait, had intended to wait and let you become more comfortable with my presence, but you belittle me, shun me and deny my very possibility. That will not do.”

Before Sherlock had a chance to speak or do anything more than just stand there, the bow slid across the strings once more. Then again. And again. Slowly a rhythm built and from that a melody bubbled forth, growing ever stronger and clearer. It was no piece the detective had ever heard, but it drew him in, more powerfully than the eyes had. As the music gained momentum, he let it wash over him, sinking beneath the waves of music. It should not be possible for one violin to produce such a complex melody that sounded more like it was scored for a full orchestra nor to evoke the amount of emotion that was stirring inside of him.

It took quite some time for him to come back to himself after the last of the music echoed and died out. Not that he particularly wanted to; like this he felt a contentment he hadn’t known since his days as an addict. When he managed to open his eyes, he fully expected to find himself alone in the flat, possibly back in the kitchen, bent over the microscope, even.

Instead he found himself collapsed on the floor, heaving and gasping as though he’d overexerted himself immensely, to the point that his body had given in. His limbs shook and his vision was blurry.

A surprisingly soft, given the calluses, and gentle hand cupped the side of his face, thumb gently stroking as he was encouraged to lift his head. He did so, expression slightly bleary and dumbfounded. Normally so carefully controlled, he couldn’t find it in him to care what he looked like at that moment.

He looked into the man’s face. How he had ever conceived of him as normal and un-noteworthy, as dull was beyond his comprehension. The otherworldliness of his visitor was clearly visible; in the sharpness and yet vagueness of his features, the ageless age of the face, but most of all in the eyes. The eyes were pools; not in the sappily romantic sense, but literal pools, shifting in colour constantly yet always with a sense of bottomless depths. They promised prosperity, they promised peace. They promised death. Liberating, peaceful death, sunken in their depths. Endless.

“Do you believe me now?” The voice twanged with the echoes of strings again, stronger than before, strangely mesmerizing.

Sherlock nodded, slowly as his head felt like it was made of lead, after a moment where he gathered his scattered, woolly thoughts. He did. He _did_. How could he not? He had always believed in empirical evidence and unwilling though he was to admit it, the amount of empirical evidence was overwhelming and irrefutable, even if the sum of the evidence amounted to something that everything in him declared impossible.

More than that, though, in the depths of the heart he would always claim he didn’t have he _wanted_ to believe. He wanted to believe rather desperately if it meant that he could hear that music again. If he could _play_ that kind of music himself. Suddenly he understood what was meant about teaching.

He was helped to his feet and deposited in his own chair; his limbs felt as if they belonged to someone else and so he was in no position to struggle. What struck him was how careful the other was, as though he was made of something fragile.

The man made to move away, possibly to sit in the other chair, but Sherlock got the control of one arm long enough for him to grab hold of one sleeve.

“I understand now,” Sherlock said quietly, voice raw with unshed emotion. “Teach me. _Please_!"

**Notes for the Chapter:**

> Chapters are getting longer - apologies if I keep ending on cliffhangers. There's a reason for it all ;) I kept the details on the case to a minimum on purpose as I'm not a crime drama writer.  
> If you can tell I struggled a bit with keeping some...well, *John* in the wording, apologies for that as well. 
> 
> Feedback is loved and treasured dearly, including concrits ;)

**Author's Note:**

> Do look up the Nøkken (apologies if your screen shows a symbol instead of the oe).  
> I know this is on the short side, but it will pick up in length as it goes on :)
> 
> Feedback really is loved and treasured, because that is the only way I can know whether I am going totally wrong or doing something right. :)
> 
> Oh, and I have a tumblr now: http://elphenfan.tumblr.com/ If anyone cares ;)


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